This invention was made by an employee of the United States Government and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or thereof.
1. Field of the Invention
The present invention is directed to a friction stir welding device and, more particularly, to a machine tool capable of performing conventional friction stir welding while manipulating pin length in real time as well as capable of performing self-reacting friction stir welding while making real time adjustments to the distance between the upper and lower shoulders.
2. Description of Related Art
The general concept of friction stir welding is described in U.S. Pat. No. 5,460,317. Conventional friction stir welding is a process of welding component pails together using the frictional heat generated by a non-consumable tool to join work piece sections. The tool includes a pin that is inserted into the joint and a shoulder that is urged against an upper surface of the work piece. The pin and shoulder rotate to generate friction needed to create a plasticized region along the joint for the welding operation.
For conventional friction stir welding operation, a workpiece is generally supported by a rigid table or anvil typically formed with a steel plate. The anvil stabilizes the actuation force of the upper shoulder to maintain the integrity of the workpiece so that the workpiece does not bend or deform under load. In order to maximize the strength of the joint between workpiece sections, the pin should extend the entire thickness of the workpiece. U.S. Pat. No. 6,199,745 attempts to address this issue by providing a unique probe pin. This pin allows for self-reacting friction stir welding since it has a rotating bottom shoulder that cooperates with the upper shoulder. However, it makes no provision for performing conventional friction stir welding.
Other improvements have taken place in this art. U.S. Pat. No. 5,893,507 describes an auto-adjustment pin tool for friction stir welding which allows the pin to be incrementally withdrawn from the workpiece thereby eliminating craters or key holes in the weld after completion of the weld. While this design may be effective for conventional friction stir welding, it makes no provision for self-reacting friction stir welding.
U.S. Pat. No. 5,697,544 shows an adjustable pin for a friction stir welding tool which allows the shoulder to move relative to the pin tool. This design makes no provision for self-reacting friction stir welding.
Accordingly, there exists a need for a tool and method for performing both conventional and self-reacting friction stir welding which will provide for the adjustment of the pin length in real time during conventional welding as well as for the adjustment of the distance between the upper and lower shoulders in real time during self-reacting friction stir welding.
An object of the present invention is to provide a tool which can perform both conventional friction stir welding (FSW) as well as self-reacting friction stir welding (SR-FSW).
Another object of the present invention is to provide a method for providing FSW and SR-FSW utilizing auto-adjustable pin tool (APT) technology as well as an ability to adjust the distance between opposing shoulders when performing SR-FSW.
Another object of the present invention is to provide a dual capability machine tool not known in the art to provide both FSW and SR-FSW capability.
Another object of the present invention is to incorporate auto-adjustable pin tool (APT) technology into a machine tool for performing either FSW or SR-FSW processes.
Another object of the present invention is to provide a tool having the ability to provide a replaceable upper shoulder and pin and/or to add and subsequently remove a lower side shoulder from the pin so that a single tool can be utilized to perform conventional as well as self-reacting FSW.
By providing this capability in a FSW device, it is believed that a significant reduction in costs can be experienced by a facility contemplating the purchase of conventional FSW equipment as well as SR-FSW equipment. The tool is preferably equipped with a replaceable upper shoulder and pin and/or a pin configured to receive a removable lower shoulder. Accordingly, a single tool may be utilized for both FSW and SR-FSW operations. A closed-loop control system allows the position and/or load on each shoulder (in SR-FSW), or on the upper shoulder and pin (in conventional FSW), to be controlled independently or in unison.